Project Summary/Abstract This R34 resubmission proposes to develop and examine a mental health service model for families of infants/toddlers with developmental delay that reduces risk for mental health problems, and in turn, enhances readiness for preschool. Infants/toddlers with developmental delay exhibit significantly higher rates of disruptive behaviors, peer problems, impulsivity, and academic failure. Their parents also are at elevated risk for mental health problems and child maltreatment. Families of infants/toddlers with developmental delay are more likely to live in poverty with limited access to services, and most receive government-funded, home- based Early Intervention (EI) services (i.e., Part C of the Individuals with Disabilities Education Act). We propose to leverage the unique position of Infant-Toddler Developmental Specialists (ITDS), front-line providers of EI services, to support parent-infant/toddler interactions and reduce family risks for mental health problems. Based on a rich empirical literature, we selected Child-Directed Interaction (CDI), the first phase of Parent-Child Interaction Therapy, as an evidence-based intervention to increase positive parent-infant/toddler interactions and reduce negative interactions. CDI aligns with the training, role, and function of ITDS, and responds to the needs of referred families. We will collaborate with EI provider agencies toward a service model that emphasizes initial training, ongoing supervision, and quality assurance to facilitate infant/toddler mental health (social, emotional, behavioral competence) and parent mental health (anxiety/depression, parenting stress, caregiver strain). We will examine feasibility, fidelity, and acceptability of the proposed model to identify facilitators and barriers to service delivery, and we will examine its promise compared to services as usual (n = 4 agencies, 16 ITDS, 112 families). In light of the extensive needs and depleting resources faced by families of infants/toddlers with developmental delay, the proposed work provides a unique opportunity to enhance the natural role and capacity of a skilled EI workforce to provide high quality services that minimize mental health problems and facilitate healthy child and family trajectories.